Review: Foxeer F722 Dual Flight Controller

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The brand new Foxeer F722 Dual flight controller has just landed and I can’t wait to find out what new features it brings to the table. In this review we will take a close look at the spec and build quality, and how it performs in a mini quad.

There is no accessories included with the F722 Dual FC, you will need your own standoffs. It comes pre-flashed with Betaflight 4.0. Note that it’s not an “AIO” FC and doesn’t have integrated PDB as it’s optimized for 4in1 ESC’s.

Big thumb up to the red PCB color, and all the clarly labelled solder pads. Overall that’s very good build quality from first impression.

It has an F7 processor, which is the type of flight controller I recommend today. Not only F7 is faster, all of its UART’s can handle both inverted and uninverted signals. This is especially handy for Frsky users because it means you can connect SBUS and SmartPort without worrying about signal inversion. F7 FC’s also have more available UART’s than F3 and F4 generally speaking.

There is a 4in1 ESC header on the FC, unfortunately the cable isn’t provided (though it normally comes with a 4in1 ESC). The good news is, you can also “direct solder” the wires to the breakout pads on the other side of the header. This makes it easy to use especially with separate ESC’s.

However, I am a bit disappointed by the lack of ESC telemetry pin in the ESC header.

There are onboard 5V and 9V voltage regulators. You can choose to power your camera and VTX with either 5V or 9V by bridging the right pads. By default, 5V is chosen for camera, and 9V is selected for VTX.

They claim there are 5 UART’s, but interestingly two of the UART’s are incomplete: UART#1 only has TX1, and UART#4 only has RX4.

The rest of the spec are pretty standard.

How’s the Board Layout?

I’d say this board has pretty good layout – camera pinout at the front (VCC, GND, Signal and camera control). and VTX pins on the right side (although I prefer to have this at the rear).

All the solder pads are well-sized and seem to be easy to work with, and are also accessible from both sides of the board for flexible wiring.

Here is an example wiring diagram provided by Foxeer.

Why Two Gyro’s?

Foxeer: “Dual Gyroscopes – MPU6000 and ICM20602 built in to give both smooth and high-speed flying experience”

From my understanding, “Dual Gyro” is the biggest selling point of the Foxeer F722 Dual FC, that’s why it’s called “Dual” right?

And yet, I think they might have headed the wrong direction, or to be more precise, they are a bit too late to the game. I have to back off a little and provide some background info here.

So the two popular gyro options for mini quad flight controllers are the MPU6000 and ICM series (including the ICM20602). The MPU6000 is slower (allows for up to 8K sampling rate), but it’s more robust against noise. The ICM gyro is faster and can run up to 32KHz, but it more susceptible to noise. Therefore many FC manufacturers went for the MPU6000 even that means sacrificing the ability of running 32KHz.

Later after some investigation, it turned out the problem wasn’t really the gyro, but simply bad FC design. To be more specific, it was the power to the gyro that was causing problem. As far as I know, major FC manufacturers have figured this out including Airbot and CL Racing, so we should expect FC’s with ICM gyro (from these companies) to perform similarly to the MPU6000 in terms of noise level going forward.

What Foxeer did here, would have made sense a year ago: you could choose to run ICM20602 for 32K or 16K looptime, or the MPU6000 for cleaner gyro. In fact, that’s not really a new idea at all, it has been done before in the Betaflight F7 by FPVModel. However, I don’t think the benefit is there anymore by having two gyros. Oh well, looking at the bright side, at least you have a backup gyro now in case the other fails right? :)

Actually, there are FC’s that use two gyro’s simultaneously (not one at a time!). Take the SP Racing F7, it uses data from both gyros and performs clever tricks like averaging or something to minimize the noise in the data. That would be the kind of innovation we want to see more in the future!

How to Choose Gyro?

By default the Foxeer F722 Dual FC uses the MPU6000 gyro. If you wish to use the ICM20602, you can select it in the CLI by entering:

set gyro_to_use = SECOND
save

Where

FIRST = MPU6000

SECOND = ICM20602

Conclusion

Good

Two onboard gyros, you have a spare one as backup – you can also choose which one to use based on how noisy your quadcopter build is

A few bucks cheaper than most other F7 FC’s out there at the moment

Pretty good layout

9V BEC for FPV VTX/Camera

Things to improve

No ESC telemetry pin in the 4in1 ESC header

No accessories, not even cables and standoffs

Soft-mount grommets are too long for nylon standoff with standard length thread – It would have been nice if they included standoffs with long enough threads

They should have just made sure gyro power is fixed, and use ICM gyro to allow for up to 32KHz; I’ve flown the CL Racing F7 in 32K and it’s very smooth even with bent props and without extra caps – this would have freed up more space as well as lowering the cost by a dollar or two